Author(s): M Chiarelli; D F Vetsch; R M Boes; C Munch-Alligne

Linked Author(s):

Keywords: Pelton runner; Modal analysis; Predictive maintenance; Finite element method; Vibration modes

Abstract: In the context of predictive maintenance, the development of new tools is crucial to assess the health-state of power units components and eventually anticipate downtime. Vibration-based condition monitoring already demonstrated efficient methods to anticipate failure and to detect changes in the vibration behaviour of structures. This numerical study focuses on the dynamic behaviour of a Pelton runner, with 22 buckets and a specific speed nq = 7.54 rpm. In a first step, a finite element method modal simulation was performed on a single bucket to capture pure-bucket modes. Then, similar simulations of the full runner demonstrated that for a given pure-bucket mode, there are 12 (11+1) occurrences of the same mode for the runner, each distinguished by their number of nodal diameter(s). Vibration modes with more than 8 nodal diameters present small variations between their natural frequencies. This can be explained by the proximity between these mode shapes and pure-bucket mode shapes. In addition, by testing two boundary conditions on the runner, it appears that preventing the displacement of the runner bores mainly impacts natural frequencies for modes with less than 4 nodal diameters.

DOI: https://doi.org/10.1088/1755-1315/1483/1/012015

Year: 2023